Impact of permafrost thaw on the turbidity regime of a subarctic river: the Sheldrake River, Nunavik, Quebec

Maxime Jolivel,Michel Allard

doi:10.1139/as-2016-0006

Abstract

In order to assess the impact of seasonal active layer thaw and thermokarst on river flow and turbidity, a gauging station was installed near the mouth of the Sheldrake River in the discontinuous permafrost zone of northern Quebec. The station provided 5 years of water level data and 3 years of turbidity data. The hydrological data for the river showed the usual high water stage occurring at spring snowmelt, with smaller peaks related to rain events in summer. Larger and longer turbidity peaks also occurred in summer in response to warm air temperature spells, suggesting that a large part of the annual suspension load was carried during midsummer turbidity peaks. Supported by geomorphological observations across the catchment area, the most plausible interpretation is that the rapid thawing of the active layer during warm conditions in July led to the activation of frostboils and triggered landslides throughout the river catchment, thus increasing soil erosion and raising sediment delivery into the hydrological network. These results indicate that maximum sediment discharge in a thermokarst-affected region may be predominantly driven by the rate of summer thawing and associated activation of erosion features in the catchment.

Highlights

Rivers are natural pathways from land to sea that carry sediments and other matter eroded from their catchments
In order to assess the impact of seasonal active layer thaw and thermokarst on river flow and turbidity, a gauging station was installed near the mouth of the Sheldrake
The Sheldrake is among many rivers of the east Hudson Bay watershed, including large fluvial systems such as the Nastapoka River that transport sediment resulting from https://mc06.manuscriptcentral.com/asopen-pubs erosional, thermokarst and periglacial processes (Fig. 2).Typically, in summer conditions, the river varies in width from 25 to 50 m

Summary

Introduction

Rivers are natural pathways from land to sea that carry sediments and other matter eroded from their catchments. Their behavior reflects different geomorphic and biogeochemical processes in the landscape with cascading effects downstream to the https://mc06.manuscriptcentral.com/asopen-pubs coastal marine environment. The riverine hydrological regime is strongly linked to seasonal climate variations, which generate a large annual range in water discharge (Déry et al 2005). The hydrological cycle of high latitude rivers is regulated by snow storage and melting and by the freezing of soil water. Permafrost is a major factor that restricts infiltration and percolation at depth; a perched water table is maintained in the active layer near the surface in summer (Carey and Woo 2001; Carey and Quinton 2005; Quinton and Carey 2008).

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